Mössbauer Spectrometry Study of Thermally-Activated Electronic Processes in Li_xFePO_4
- Creators
- Tan, H. J.
- Dodd, J. L.
- Fultz, B.
Abstract
The solid solution phase of Li_xFePO_4 with different Li concentrations, x, was investigated by Mössbauer spectrometry at temperatures between 25 and 210 °C. The Mössbauer spectra show a temperature dependence of their isomer shifts (E_(IS)) and electric quadrupole splittings (E_Q), typical of thermally activated, electronic relaxation processes involving ^(57)Fe ions. The activation energies for the fluctuations of E_Q and E_(IS) for Fe^(3+) are nearly the same, 570 ± 9 meV, suggesting that both originate from charge hopping. For the Fe^(2+) components of the spectra, the fluctuations of E_Q occurred at lower temperatures than the fluctuations of E_(IS), with an activation energy of 512 ± 12 meV for E_Q and one of 551 ± 7 meV for E_(IS). The more facile fluctuations of E_Q for Fe^(2+) are evidence for local motions of neighboring Li^+ ions. It appears that the electron hopping frequency is lower than that of Li^+ ions. The activation energies of relaxation did not have a measurable dependence on the concentration of lithium, x.
Additional Information
© 2009 American Chemical Society. Received: September 26, 2008; Revised Manuscript Received: November 27, 2008. Publication Date (Web): January 15, 2009. The authors thank Dr. Amine, Dr. Belharouak, and Argonne National Laboratory for providing the LiFePO_4 material. H.T. thanks J. Y. Y. Lin and L. Mauger for their help with the computational work. The authors thank General Motors for financial support.Additional details
- Eprint ID
- 15549
- Resolver ID
- CaltechAUTHORS:20090902-083907646
- General Motors
- Created
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2009-09-09Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field